The present disclosure relates to automotive arts, the signal processing arts, sensor arts, airflow arts, internal combustion engine arts, and the like.
Performance intake systems, or “cold air intakes,” are very popular in the automotive aftermarket. These systems reduce pressure drop and supply cooler airflow to an internal combustion engine. This results in more efficiency and increased engine power. Tighter emission standards promulgated by environmental agencies are, however, making the manufacture of performance intake systems that require a mass airflow sensor difficult.
When an engine control system is being designed for a production vehicle, a mass airflow sensor, intake tube, and airbox are assembled to fit a particular engine. When this system is complete, the entire intake system is tested on a precision flow stand to extract the mass airflow sensor transfer function. This mass airflow transfer function is a set of voltage or frequency readings taken at different specific air flows. The data thus collected is used by the engine control system to control ignition timing, required fuel, and multiple emission parameters. Because of heightened emission standards, changes to emission parameters from aftermarket intake systems may cause a vehicle using such an aftermarket system to be noncompliant.
Most modern vehicles use an insert type of mass airflow sensor. This sensor is designed to be installed into the vehicle's air box. Normally, when an aftermarket intake system is designed, it is designed with larger diameter tubing and a higher flowing air filter. Since the output of a mass airflow sensor is proportional to the area of the tube into which it is installed, aftermarket intake system designers will select a portion of their intake tube and reduce that tube to the original size that the factory mass airflow sensor was originally installed into.
This process will generally reproduce the original equipment manufacturer (OEM) intake mass airflow transfer function, but because of the different airflow profiles at different velocities, it is not perfect. In the past, these manufacturers relied on oxygen sensor feedback and fuel trims to correct for this transfer function error.
The problem with this method is that it only corrects for proper air/fuel ratio. The MAF sensor is also used for calculating engine load, ignition timing, and multiple emission functions. In particular, more strict and demanding emission requirements are making it impossible for these aftermarket intake systems to pass EPA requirements.
What is needed is a system, method, and apparatus that will enable the manufacture of performance air intake systems which accurately measure the mass airflow into the engine.